Gaseous fuel engines are well known in the art. They typically burn readily available natural gas but are capable of burning any suitable gaseous fuel such as butane, propane, methane or even hydrogen. Examples of typical gaseous fuel engines include the series G 3600 gaseous engines manufactured by Caterpillar, Inc. These engines are relatively large and stationary, and are often utilized to power generators and pumps, etc. These Caterpillar gaseous engines are capable of producing power in excess of 1200 horsepower up to about 4700 horsepower provided that the engine is supplied with an adequately pressurized source of gaseous fuel.
In order to put any substantial load on a gaseous engine of the type to which the present invention relates, the gaseous fuel supply pressure must at least be on the order of about 15 psig. Under full load conditions, the engine can require a gaseous fuel supply in excess of about 45 psig. Often because of safety regulations or other limitation factors, the available gaseous fuel supply is often less than about 2 psig. When the gaseous fuel is supplied at such a relatively low pressure, some means must normally be provided to raise pressure sufficiently to operate the gaseous engine with a substantial load. At the present time, those skilled in the art typically employ one of two different methods for raising fuel pressure, both of which suffer from relatively severe drawbacks.
In the first prior art method of raising fuel pressure, air and fuel are mixed at ambient pressure and then compressed as a mixture by a turbocharger attached to the exhaust from the engine. Because the compressed mixture is not only flammable but explosive, extreme precautions must be taken in order to prevent ignition and or leakage of the compressed air/fuel mixture. Because of the potential catastrophic consequences, this method of raising fuel pressure is extremely undesirable. In the more practiced prior art method of raising fuel pressure, a separate compressor unit is employed to generate a reservoir of gaseous fuel that is maintained at about 45 psig. While this method is considerably safer than the other prior art pressure raising method, it is undesirable because of the added expense and complexity in operating a separate compressor unit. In many cases this option is also undesirable because the compressor is either driven mechanically by the engine or by electricity produced by the engine. This undesirable load on the engine lowers the available horsepower to do other work.
The present invention is directed to overcoming these and other problems associated with air and fuel supply systems for gaseous engines.